/*
 * =============================================================================
 * Copyright by Benjamin Sempere,
 * All rights reserved.
 * =============================================================================
 * Author  : Benjamin Sempere
 * E-mail  : benjamin@sempere.org
 * Homepage: www.sempere.org
 * =============================================================================
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package org.sempere.commons.velocity;

import org.apache.velocity.*;
import org.apache.velocity.app.*;
import org.slf4j.*;

import java.io.*;
import java.util.*;


/**
 * Helper class that provides methods to work with Apache Velocity Framework.
 *
 * @author sempere
 */
public final class VelocityHelper {

	private static final Logger LOGGER = LoggerFactory.getLogger(VelocityHelper.class);

	// *************************************************************************
	//
	// Constructors
	//
	// *************************************************************************

	private VelocityHelper() {
	}

	// *************************************************************************
	//
	// Convenience methods
	//
	// *************************************************************************

	public static String transform(String templatePath, Map<String, Object> engineConfigurationMap, Map<String, Object> contextMap) {
		try {
			// Engine configuration
			VelocityEngine engine = new VelocityEngine();
			for (Map.Entry<String, Object> entry : engineConfigurationMap.entrySet()) {
				engine.setProperty(entry.getKey(), entry.getValue());
			}
			engine.init();

			// Context configuration
			VelocityContext context = new VelocityContext();
			for (Map.Entry<String, Object> entry : contextMap.entrySet()) {
				context.put(entry.getKey(), entry.getValue());
			}

			// Engine execution
			Writer writer = new StringWriter();
			engine.getTemplate(templatePath).merge(context, writer);

			return writer.toString();
		}
		catch (Exception e) {
			LOGGER.error("Could not execute velocity transformation.", e);
			return null;
		}
	}
}